1/2 inch behind the spar is where I would like to have it CG. I installed ALU. landing gear and add some support to the landing gear area(front). I think this is what has me off so bad. She CG perfect when the battey is placed behind the f3 bulk head. This will require a little cutting and time. I would add some weght to the tail, but she is off bad. I laid 3 1/2 oz that did not do the trick, so I decied to take the battery position option. Thanks I will report!